This invention relates generally to mechanisms for mixing a powder with a liquid to form a homogeneous mass, and more particularly to a high-speed, fully automatic dough processing apparatus.
While the invention will be described in connection with the production of dough for making bakery products such as bread, pizza and pastry, it is to be understood that the mixing mechanism included in the apparatus has many other practical applications unrelated to bakery products.
From the standpoint of production volume, bread is the most important baked product. Mixing is the first active step in bread production. The ingredients involved in mixing are flour and a dough-forming solution constituted typically by water, yeast, sugar, salt, milk and shortening. Ideally, mixing should result in a uniform mixture forming a smooth dough; it should develop the gluten in the dough in order to promote the elasticity of the dough and permit it to retain the gases generated by the yeast; and it should distribute the yeast cells uniformly so that they will receive proper nutrition.
In traditional techniques for producing dough, such as the batch method which uses heavy blades revolving in a large bowl to mix the flour and dough-forming solution into a homogeneous mass, a number of steps must be separately performed which render the process time-consuming and costly. Moreover, the resultant dough is not entirely homogeneous, giving rise to non-uniform dough balls and a final baked product of unpredictable consistency.
In my prior U.S. Pat. No. 3,888,997, entitled "Method and Apparatus for Processing Dough," there is disclosed a mechanism operating at exceptionally high speed to effect continuous mixing, all necessary steps being carried out automatically from the initial step of feeding the flour and the dough-forming solution into the machine to the final step of forming divided units of the processed dough ready for baking. This patented mechanism obviates many of the drawbacks experienced with conventional techniques.
In my prior patent, whose entire disclosure is incorporated herein by reference, a screw rotating within a vertical tubular chamber acts to centrifugally hurl flour fed into the chamber against the inner wall thereof, thereby depositing a thin film of flour on the inner wall. Also fed into the chamber is the dough-forming solution which is hurled centrifugally against the thin film of flour to form on the inner wall a pasty film which is directed downwardly along a helical path. The pasty film is scraped from the inner wall to produce a downwardly-extending ribbon that is subjected to a kneading action.
The flour fed into the mixing chamber is introduced therein through a hopper having an outlet of fixed dimensions. The practical difficulty with this fixed feed arrangement is that it fails to take into account the changing flowability of flour with variations in ambient temperature and humidity. It also does not accommodate the feed to the disparate characteristics of various flours. One, therefore, is not always able to attain optimum flour flow conditions.
Flour, which is a finely ground meal of wheat, is the backbone and structure of baked goods, flour acting both as a binding and absorbing agent. Wheat is the only cereal that contains the proper combination of glutenin and gliadin for bread-making. When combined with water, these constituents form gluten which is essential for retaining the gas produced by yeast.
However, the form of wheat used depends on the ultimate product. Thus there are several kinds of so-called hard wheat, the choice depending on the final product (i.e., rolls or bread). Cakes and cookies are derived from various types of soft wheat. In some instances, rye flour milled from rye grain may be blended into wheat flour.
The need exists, therefore, for means to adjust the feed of flour in an arrangement of the type disclosed in my prior patent to accommodate the machine to changing ambient conditions and to different flour characteristics.
Also in my patented machine, because it operates continuously, it is desirable that the dough-forming solution also be produced continuously in accordance with the demand of the machine rather than on a batch basis. When combining water, yeast and other ingredients in a mixing tank and then pumping the solution from the tank into the dough-forming machine, this necessarily results in a relatively prolonged interaction period within the tank, particularly with respect to that portion of the solution which is the last to be drawn therefrom. This prolonged interaction period may have deleterious effects with certain types of yeast, particularly instant yeast.
And while may patented machine includes a proofing tube through which processed dough leaving the chamber flows on its way to a cutting station, the proofing tube does not include means to heat the dough to the temperature best suited for proofing.